Titration of a Diprotic Acid2

Titration of a Diprotic Acid2 - Michelle Chavdar March 30,...

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Michelle Chavdar March 30, 2008 AP Chemistry 4 Titration of a Diprotic Acid: Identifying an Unknown I. Purpose: The purpose of this lab is to identify an unknown diprotic acid by finding its molecular weight. II. Procedure : Weigh out 0.120 g of the unknown diprotic acid and record its mass to the nearest thousandth of a gram. Fill a 250 mL beaker with 100 mL of distilled water, and put the unknown acid into the beaker to be dissolved. Next, add a stirring bar and place the beaker on the magnetic stirrer. Suspend a pH sensor, on a ring stand, in the diprotic acid solution. Turn the stirrer on to medium. In a 250 mL beaker obtain 60 mL of 0.1 M NaOH solution. Next rinse a 50 mL buret with the 0.1 M NaOH, and record this concentration in the data table. Suspend the buret on the ring stand so it’s over the beaker. Fill the buret above the 0.00 mL mark with 0.1 M NaOH. Level and drain the buret to 0.00 mL. Now connect the pH sensor to the computer and open the file “25a Titration Dip Acid.” This file can be found in the Chemistry with Computers folder in the program Logger Pro. Before adding the NaOH click the COLLECT button and monitor the pH for about five seconds to make sure it stabilizes. Once it’s stable, click the KEEP button, and type “0” in the edit box and press ENTER. Now add NaOH until the pH goes up by 0.20 and wait for the pH to stabilize. Once stabilized, click the KEEP button. Next, type the current buret reading, to the nearest 0.01 mL, in the edit box and press ENTER. Keep adding NaOH so that the pH of the solution continues to rise by 0.20 units and enter the volume of the buret after each reading. Continue doing this until the pH reaches 3.5. Once 3.5 are reached, add 2-drop increments instead of the other method. Continue to enter the buret reading after each increment. Once the pH reaches 4.5 return to the previous method of increasing by 0.20. Continue this process until a pH of 7.5 is reached. Once 7.5 are reached, return to the 2-drop method. Continue until a pH of 10 is reached. Once 10 are reached, return to the method that increased the pH by 0.20
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Titration of a Diprotic Acid2 - Michelle Chavdar March 30,...

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